Secondary battery with advanced safety

Abstract

Disclosed herein is a secondary battery constructed in a structure in which an electrode assembly having a cathode / separator / anode arrangement is mounted in a battery case made of a laminate sheet including a resin layer and a metal layer, electrode tabs of the electrode assembly are coupled to corresponding electrode leads, and the electrode assembly is sealed in the battery case while electrode leads are exposed to the outside of the battery case, wherein a protective film is attached to coupling regions between the electrode tabs and the electrode leads for sealing the coupling regions between the electrode tabs and the electrode leads. The secondary battery according to the present invention is constructed in a structure in which the coupling regions are sealed by the protective film, unlike a conventional secondary battery constructed in a structure in which the coupling regions between the electrode tabs and the electrode leads are exposed in the battery case. As a result, the electrode leads are protected from external impacts, such as falling of the battery. Consequently, no internal short circuit occurs, and therefore, the safety of the battery is increased.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims priority from Korean Patent Application No. 10-2005-0106296 filed on Nov. 8, 2005, the disclosure of which is hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a secondary battery with improved safety, and, more particularly, to a secondary battery constructed in a structure in which an electrode assembly having a cathode / separator / anode arrangement is mounted in a battery case made of a laminate sheet including a resin layer and a metal layer, electrode tabs of the electrode assembly are coupled to corresponding electrode leads, and the electrode assembly is sealed in the battery case while electrode leads are exposed to the outside of the battery case, wherein a protective film is attached to coupling regions between the electrode tabs and the electrode leads for sealing the coupling regions between the electrode tabs and the electrode leads, and therefore,...

AI Technical Summary

Benefits of technology

The present invention relates to a battery with improved safety. The inventors found that when the coupling regions between electrode tabs and electrode leads are sealed by a protective film, the occurrence of internal short circuits is prevented. The electrode tabs extend a long distance from the electrode current collectors to avoid damage to the separators. The protective film is attached to the coupling regions to prevent contact between the coupling regions and the battery assembly. The use of the protective film improves the safety of the battery. The electrode tabs and the coupling regions can be sealed by attaching two-unit film members or winding one-unit film members on the welded parts. The electrode tabs extend a predetermined length to prevent damage to the separators.

Problems solved by technology

When a lithium secondary battery, such as the lithium-ion polymer battery, is exposed to high temperature, or when a large amount of current flows in a short time due to overdischarge, an external short circuit, a nail penetration, a local crush, or a drop-induced short circuit, the battery is heated due to IR heat generation with the result that the battery may catch fire or explode.

This vicious cycle causes a thermal runaway phenomenon in which the temperature of the battery is sharply increased.

When the temperature of the battery is increased to a predetermined temperature level, the battery may catch fire.

When the internal pressure of the battery is increased to a predetermined pressure level, the lithium secondary battery may explode.

This possibility that the lithium secondary battery catches fire and explodes is the most fatal disadvantage of the lithium secondary battery.

Especially, the battery case of the lithium-ion polymer battery is made of a soft wrapping material having low strength.

As a result, the battery case of the lithium-ion polymer battery is easily deformed when the battery falls or external impacts are applied to the battery.

The falling of the battery frequently occurs during the use of the battery.

However, these methods have a problem in that the adhesive tape and the foreign material chemically react with the electrolyte, and therefore, the performance of the battery is reduced.

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